ARDUINO M0 BOOTLOADING FAILED

Hi,
I'm trying to boot load ATSAMD21G18A using ATMEL-SAM ICE but it doesn't works, i tried with several bootloader files, all the hex file is loded succesfully using atmel studio but when i connect the usb to the m0 it doesnt show anything in device manager can any one please help.

Hi.

Well I look like an idiot after the threads are merged. In the spirit of being helpful:
It sounds like you might be using a custom board rather than an Arduino. Please post a schematic.
Have you tried burning the bootloader using the Arduino IDE?